1. Field of the Invention
The present invention relates to a circuit breaking device incorporated into an automobile and others.
2. Description of the Related Art
Concerning this type circuit breaking device, it is common to use a fuse or a fusible link incorporated into an electric circuit so that the current flow in the circuit is interrupted when excessive current is generated in the electric circuit. On the other hand, in case of an emergency such as an automobile accident, it is necessary to forcibly shut off the electric circuit in a moment. For example, in an electric power supply circuit of an electric automobile which has come into wide use recently, there is a strong demand for forcibly shutting off the electric circuit in a moment in case of emergency.
As disclosed in Japanese Examined Patent Publication No. 58-47809, the conventional circuit breaker of this type is activated in such a manner that an electric conductor incorporated into an electric circuit is forcibly broken by an explosive force. As shown in FIG. 10, this circuit breaker is composed as follows:
In a reinforced glass case 105, there are provided a fuse 102 connected between output terminals 101, an explosive 103, and a filament 104 for heating this explosive 103. When an electric current generates in the input terminals 106, this filament 104 is heated, so that explosive 103 is exploded. Utilizing the explosive force, the fuse 102 is broken. Due to the above structure, it is possible to forcibly shut off the electric circuit at an arbitrary time.
However, according to the conventional circuit breaker, the following problems may be encountered. The explosive force of explosive is dispersed in all directions, and only one portion of the explosive force acts on the fuse 102. Therefore, a considerably high intensity of explosive force is required for breaking the fuse 102 positively. Therefore, the sealed glass case 105 must have a strong structure so that it can withstand a high intensity of explosive force. Further the sealed glass case 105 must be subjected to a special treatment for enhancing the mechanical strength. Accordingly, the manufacturing cost is inevitably increased. Additionally, the conventional circuit breaker is disadvantageous in that it is not simple to reset the circuit breaker after the fuse 102 has been broken. Thus, after an electric automobile has been involved in an accident, it is impossible to reset the circuit breaker immediately so that the electric automobile can be moved under its own power.